Pictures showed there had been at least five different landslides, some having uprooted trees and carried rocks down the hillside.

One man, gesturing to the mud-covered remains of a house, told NHK: "My house is over there, flattened."

Pointing elsewhere, he said: "A leg was seen [sticking out of the mud] and they are trying to confirm if the person is alive. The first thing we have to do is to help that person."

Japanese troops were deployed in response to a request from the local government.

Prime minister Shinzo Abe said there would be a sizeable response.

"I have ordered [government officials] to carry out the rescue operation in an integrated manner, aware of the possibility of further rain," he said in Tokyo.

"I also ordered them to raise the number of Self-Defence Force personnel to several hundred in order to strengthen rescue operations," he said, adding he would be sending one of his ministers to the site.

Japan's weather agency warned more heavy rain was on the way to the area, raising the risk of further landslides in places where tonnes of mud have already been displaced.

With land in short supply in many parts of Japan, cities often expand into mountainous areas, leaving such developments vulnerable to landslides.

The archipelago has been battered in recent weeks by unusually heavy rain that has sparked a number of smaller landslides and several floods, some of which have claimed lives.

Despite widespread concreting to shore up hillsides, mountainous and densely populated Japan is prone to this kind of disaster.

In October last year, dozens of people were killed when the torrential rains of a passing typhoon triggered large landslides on the island of Oshima, south of Tokyo.